that president obama will travel to boston for an interstate service on thursday. laura joins us from a city still in shock. >> yes, cathy, a very somber city. as you just heard in the update from fbi officials in boston, someone knows who did this. they said they are appealing to the public for clues. we also have an update on the forensic examination of the site where the bomb went off. it seems the bomb was contained in a pressure cooker and carried in a black nylon backpack.